Yield Gap and Water and Fertilizer Use Efficiency Gap for Maize on the Upland China

Maize (Zea mays L.) is one of the main agricultural crops with the largest yield and acreage in the Upland China. The improvement of the yield and yield gap(YG) of Maize has been receiving increasing research attention. This study offers a theoretical foundation for enhancing maize yield and optimizing water use efficiencie (WUE) and fertilizer use efficiencies in major grain-producing regions. It specifically investigated the impact of various cultivation methods on maize yield and the WUE and fertilizer use efficiency in the arid regions of Gansu, ultimately identifying the most effective modes of cultivation. This study was conducted in the regions of Zhenyuan and Dingxi, Gansu Province, China, from 2018 to 2020. Dryland maize comprised four modes of cultivation management for planting density, fertilizer application, and mulching method—basic yield level (CK), farmer level (FP), high yield and high-efficiency level (HH), and super high yield level (SH). YSH, YHH, YFP, and YCK comprised 32.57%, 45.00%, 56.50%, and 67.03% (Zhenyuan) and 47.97%, 58.52%, 63.94%, and 80.06% (Dingxi) of YHR. The YG between maximum yield (YHR) and SH yield (YSH), YSH and HH yield(YHH), YHH and FP yield(YFP), and YFP and CK yield(YCK) were found to be 11.89t.ha-2 , 2.56t.ha-2 , 2.54t.ha-2 , 2.95t.ha-2. The current uncontrollable factor contribution rate for the YG was 59.12%, the contribution rate of the controllable factor for the yield gap was 40.88%. This indicates a huge scope for improvement in the maize yield per unit area in Gansu. The water use efficiency gap (WG) between SH and HH, HH and FP, and FP and CK were 7.15kg.mm-1. ha-2 , 4.34kg.mm-1 .ha-2 and 10.52kg.mm-1 .ha-2. The nitrogen partial productivity gap (PFPGN) between SH and HH, and HH and FP were determined to be 5.41kg.kg-1 and 13.13kg.kg-1 , respectively, while the phosphorus partial productivity gap (PFPGP) was 9.46kg.kg-1 and 21.43kg.kg-1. The YG exhibited a positive correlation with the WUEG while demonstrating a negative correlation with both the PFPGN and PFPGP. Among the different regions studied, Gansu Province demonstrated the highest yield and WUE for upland maize under super-high-yield conditions. The study revealed that the highest partial productivity of nitrogen and phosphate fertilizers was observed at the farmer level. Consequently, it is imperative to enhance fertilizer use efficiency in SH and HH modes to achieve further increases in crop yield. This improvement is particularly crucial for dry maize production, as it plays a significant role in safeguarding national food security.